This application is the National phase of International Application PCT/JP00/02151, filed Apr. 3, 2000, which designated the U.S. and that International Application was not published under PCT Article 21(2) in English.
The present invention relates to a hollow fiber membrane module having superior chemical resistance used for deaeration treatment of chemicals in a semiconductor production process, printers, liquid crystal sealing process or chemical production process and so forth, its potting material and a chemical deaeration method using said hollow fiber membrane module.
This application is based on Japanese Patent Application No. Hei 11-97064 and Japanese Patent Application No. Hei 11-132580), the contents of which are incorporated herein by reference.
In a semiconductor production process, a photoresist liquid is coated onto a thin film laminated onto a semiconductor wafer, and after exposing and developing through a mask in which a pattern is formed, is etched to form a pattern in the thin film.
At this time, in the developing step, a developing solution (chemical) is typically pumped to a discharge nozzle with nitrogen gas and discharged from that nozzle to spin coat developing solution onto the semiconductor wafer. However, the pressure applied to the chemical when discharged from the nozzle may return to atmospheric pressure resulting in the supersaturated dissolved gas forming bubbles. If the developing solution is spin coated onto the semiconductor wafer while still containing bubbles, development is incomplete resulting in the occurrence of undeveloped portions. Thus, it is necessary to deaerate the nitrogen gas that is dissolved in the chemical pumping step to inhibit the formation of bubbles.
Moreover, in a semiconductor production process, in a step in which an interlayer insulating film is coated followed by cutting away the non-flat portion around the film (edge rinsing step), work is performed in which a solvent (consisting primarily of alcohol) is dropped onto the film to dissolve the peripheral edge of the film. In addition, in an edge rinsing step performed in the same manner as in the case of the above interlayer insulating film after having coated a thin film having a low dielectric constant, work is performed in which a solvent (such as alcohol, ether, ketone or hydrocarbon) is dropped onto the film to dissolve the peripheral edge of the film. In these steps, the solvent that is used is also pumped with nitrogen gas. Consequently, bubbles may form when the pressure is released thereby resulting in the formation of bubbles along with the splashing of liquid droplets onto the film causing the occurrence of defects. Thus, in order to eliminate these defects, it is necessary to deaerate the gas dissolved in the solvent to inhibit the formation of bubbles.
Moreover, in addition to the developing solution and solvent mentioned above, it is also necessary to deaerate a photoresist solution as necessary.
In addition, deaeration is also performed for printer ink as well. In an ink jet printer equipped with a piezo element head, pressurization and depressurization are repeated several times by the piezo element during ink discharge. At this time, dissolved nitrogen, oxygen and other gases in the ink filled in the head grow into bubbles and these bubbles easily accumulate in the head. Consequently, these bubbles are discharged during ink discharge causing the occurrence of printing omissions.
In addition, in an ink jet printer equipped with a thermal head, gas dissolved in the ink grows into bubbles during head driving in the thermal cycle of rapid heating and cooling of the ink, and these bubbles easily accumulate in the head. Consequently, these bubbles are discharged during ink discharge causing the occurrence of printing omissions.
Thus, it is necessary to reduce the concentration of dissolved gas in the ink and inhibit the formation of bubbles by deaerating in these printers as well.
As an example of a technology relating to deaeration of dissolved gas in a chemical using a membrane, a deaerating membrane module for semiconductor developing solution is proposed in Japanese Unexamined Patent Application, First Publication No. Hei 9-187629. The deaerating membrane module disclosed here is that in which those portions of the housing and/or end caps, hollow fiber membrane and end seals that come in contact with chemical are composed of a material having superior developing solution resistance.
With respect to this deaerating membrane module, epoxy resin is used as a preferable example of the material of its sealing material (potting material). Examples of epoxy resins include glycidyl ether, glycidyl ester, glycidyl amine, aliphatic epoxide and alicyclic epoxide, while examples of curing agents include aliphatic polyamines, alicyclic polyamines, polyamide amines and polyamides.
In addition, a preferable example of a hollow fiber membrane is a heterogeneous hollow fiber membrane composed of poly-4-methylpentene-1, and having a pore-free, homogeneous thin film layer that is continuous with the surface of a porous membrane.
In addition, a method in which dissolved nitrogen in a chemical is deaerated using a non-porous (homogeneous) tube membrane, in which poly(tetrafluoroethylene) resin having superior solvent resistance is formed into the shape of a tube, is proposed in Japanese Unexamined Patent Application, First Publication No. Hei 8-243306 and Japanese Unexamined Patent Application, First Publication No. Hei 9-7936.
In addition, as an example of printer ink deaeration technology, an ink deaeration method for ink jet recording is proposed in Japanese Unexamined Patent Application, First Publication No. Hei 5-17712. This is a method for deaerating ink using a gas permeable membrane having a thickness of 10 xcexcm or less composed of polyethylene resin, polypropylene resin, poly(tetrafluoroethylene) resin, polystyrene resin, polymethyl methacrylate resin and so forth.
However, in the deaerating membrane module described in the above Japanese Unexamined Patent Application, First Publication No. Hei 9-187629, the chemical resistance of each member used in the deaerating module was evaluated according to the amount of change induced by chemical immersion for 3 months. Consequently, this method for evaluating chemical resistance was unable to accommodate members in which deterioration progresses rapidly after 3 months of immersion. Deaerating membrane modules using such members had problems with long-term stability. In addition, although each of the members of this deaerating membrane module exhibit a certain degree of resistance to alkaline chemicals like semiconductor developing solution, they were not resistant to chemicals such as alcohols, photoresist, printer ink and liquid crystal, and had problems such as swelling and elution caused by these chemicals. Consequently, this deaerating membrane module was unable to be used for deaerating chemicals such as alcohols, photoresist, printer ink and liquid crystal, etc.
In order to solve this problem, a membrane module was proposed in which the entire module is composed of thermoplastic resin having high resistance to solvents and other chemicals as proposed in Japanese Examined Patent Application, Second Publication No. Hei 7-34850, Japanese Examined Patent Application, Second Publication No. Hei 7-34851 and Japanese Unexamined Patent Application, First Publication No. Hei 1-293105. In the production of these modules, in order to separate the one side and the other of the membrane in a fluid-tight or airtight manner, a thermoplastic resin is used for the potting material when fixing the membrane to the housing, and particularly when fixing the hollow fiber membrane to the housing with the potting material. Consequently, it is essential to melt the potting material for potting processing.
However, in the case of performing potting processing by melting the potting material, it is necessary to select a hollow fiber membrane that it is able to withstand the heat during processing, thereby resulting in the problem of the hollow fiber membrane that can be used being extremely limited. In addition, the viscosity of the melted potting material is normally extremely high. Consequently, in the case of fixing hollow fiber bundles consisting of collected hollow fibers to the housing with a potting material, it becomes difficult for the resin to penetrate between the fibers resulting in the problem of the formation of xe2x80x9cloose areasxe2x80x9d in potted portions. These xe2x80x9cloose areasxe2x80x9d in the potted portions easily cause leaks.
Moreover, fluororesins are used as ideal thermoplastic resins. However, polymers of fluororesins such as PTFE are expensive, and also have the disadvantage of having comparatively low processability.
On the other hand, a module having superior solvent resistance that uses a thermosetting resin for the potting material is proposed in Japanese Unexamined Patent Application, First Publication No. Hei 6-170176. This thermosetting resin is a combination of epoxy resin and cationic polymerization curing agent or anionic polymerization curing agent. However, depending on the type of curing agent, there is concern over the risk of metal in the curing agent eluting into the chemical and causing contamination of the chemical.
Moreover, the addition of inorganic filler to the potting material is also proposed in Japanese Unexamined Patent Application, First Publication No. Hei 6-170176. However, this method also had the problem of the chemical being contaminated by metal that elutes from the filler. Moreover, even if a polyurethane resin is used for the potting material, there was also concern over elution of metal in the case of using a polyurethane resin that is cured by adding an organometallic catalyst to accelerate the curing reaction.
In addition, polyolefin having resistance to chemicals is typically used for the housing material. However, since polyolefin contains significant amounts of metals or other compounds as impurities, there was the problem of the metal in the housing eluting into the chemical when the chemical and housing came in contact. Elution of metal into the chemical has the potential to cause serious defects in the semiconductor production process. Accordingly, it is necessary to avoid contamination of the chemical by metal.
In addition, fluororesins such as PTFE are examples of materials frequently used as a chemical resistant material. However, fluororesins had the problem of being difficult to process as well as being extremely expensive.
In addition, the heterogeneous hollow fiber membrane comprised of Poly(4-methylpentene-1) mentioned above is also susceptible to the formation of communicated pores in the homogeneous thin film layer, and to the occurrence of pin holes in the homogeneous thin film layer caused by mechanical wear during handling following membrane production. Thus, in the case of such membrane, when a chemical penetrates into the porous pores by wetting the membrane material, there were cases in which the chemical leaked from the pores and pin holes in the homogeneous thin film layer.
In addition, in the case of a method using the non-porous (homogeneous) tube membrane comprised of poly(tetrafluoroethylene) resin previously described, in addition to the low nitrogen permeability coefficient of the membrane material, since the thickness of the tube is also thick, the nitrogen transmission rate is low (for example, nitrogen transmission rate 0.5xc3x9710xe2x88x9211 cm3/cm2xc2x7Paxc2x7sec) such that even if deaeration was performed, there were cases in which it was inadequate as a practical level of deaeration.
In addition, a deaeration method for the ink jet recording ink previously described consists of supplying raw material ink to the hollow portions of a hollow fiber membrane, reducing the pressure outside the membrane, and deaerating dissolved gas in the ink through the membrane. However, since the thickness of the tetrafluoroethylene tube used in its embodiments is extremely thin at 1-2 xcexcm resulting in low mechanical strength, there were cases in which the membrane ruptured due to the pressure of the raw material ink, thereby causing leakage of ink.
In order to solve the above problems, the object of the present invention is to provide a hollow fiber membrane module having superior chemical resistance by using a material having superior chemical resistance as the material of a housing that contains and protects a hollow fiber membrane and a potting material that adheres and fixes the hollow fiber membrane.
In addition, another object of the present invention is to provide a hollow fiber membrane module free of metal elution by using a material that is free of contamination by metal impurities for a potting material and housing material.
Moreover, another object of the present invention is to provide a hollow fiber membrane module having superior chemical resistance, deaeration performance and durability performance by using a hollow fiber membrane having superior chemical resistance and gas permeability, as well as a chemical deaeration method capable of efficiently deaerating chemicals.
The potting material for a hollow fiber membrane module of the present invention is characterized as being an epoxy resin cured product wherein, in a potting material for a hollow fiber membrane module that adheres and fixes a hollow fiber membrane wherein, the weight change per unit surface area of a potting material test piece after immersing said test piece in a chemical for 6 months at room temperature is within the range of xe2x88x9220 to +20 mg/cm2. This potting material for a hollow fiber membrane module has superior chemical resistance.
In addition, the potting material for a hollow fiber membrane module of the present invention is preferably an epoxy resin cured product wherein the rate of change in the thickness of a potting material test piece after immersing said test piece in a chemical for 6 months at room temperature is within the range of xe2x88x9215 to +15%. This potting material for a hollow fiber membrane module has superior chemical resistance.
In addition, the potting material for a hollow fiber membrane module of the present invention is preferably the cured product of an epoxy resin having a polysulfide skeleton in its molecule and a curing agent at least containing an aromatic polyamine. This potting material for a hollow fiber membrane module has low compatibility with solvent and is resistant to swelling caused by chemicals.
In addition, the potting material for a hollow fiber membrane module of the present invention is preferably the cured product of an epoxy resin having at least three glycidyl groups in its molecule and a curing agent at least containing an aromatic polyamine. Since this potting material for a hollow fiber membrane module has high crosslinking density, it has even more superior chemical resistance.
In addition, the content of metal present in the potting material is preferably 300 ppm or less. This potting material for a hollow fiber membrane module does not cause contamination of the chemical by metal.
In addition, the hollow fiber membrane module of the present invention is characterized by a hollow fiber membrane being adhered and fixed by the above potting material for a hollow fiber membrane module. This hollow fiber membrane module can be used in chemical treatment for a long period of time without the occurrence of leakage from the module. In addition, this hollow fiber membrane module does not cause contamination of the chemical by metal.
In addition, the hollow fiber membrane module of the present invention is characterized by its housing material being a polyolefin in which the weight change per unit surface area of a polyolefin test piece after immersing said test piece in a chemical for 6 months at room temperature is within the range of xe2x88x9220 to +20 mg/cm2, and the total content of metal present in the polyolefin is 300 ppm or less. Since the housing material of this hollow fiber membrane module has superior chemical resistance, it can be used in chemical treatment for a long period of time without the occurrence of leakage from the module
In addition, the above polyolefin is preferably such that the rate of change in the thickness of a test piece thereof after immersing said test piece in a chemical for 6 months at room temperature is preferably within the range of xe2x88x9215 to +15%. Since this polyolefin has superior chemical resistance, it is suitable for a housing material.
In addition, the above polyolefin is preferably polyethylene or cycloolefin polymer. Since this polyolefin has superior chemical resistance and has a low metal content, it is suitable for a housing material.
In addition, the hollow fiber membrane module of the present invention is characterized by a hollow fiber membrane being adhered and fixed in a housing comprised of the above polyolefin by the above potting material for a hollow fiber membrane module. Since potting material and housing material of this hollow fiber membrane module have superior chemical resistance, it can be used in chemical treatment for a long period of time without the occurrence of leakage from the module.
In addition, the hollow fiber membrane module of the present invention is preferably such that the hollow fiber membrane is a hollow fiber membrane having a composite structure in which a homogeneous thin film is juxtapositioned between porous support layers, the transmission rate ratio of the oxygen transmission rate to the nitrogen transmission rate of the hollow fiber membrane is 1.1 or more, and the rate of change in the above transmission rate ratio of after immersing in a chemical for 6 months at room temperature is within the range of xe2x88x9215 to +30%. This hollow fiber membrane module has superior chemical resistance, deaeration performance and durability performance.
In addition, the above hollow fiber membrane is preferably such that the weight change ratio of the hollow fiber membrane after immersing in a chemical for 6 months at room temperature is within the range of xe2x88x9230 to +30%. Since this hollow fiber membrane has superior chemical resistance, it can be suitably used in the hollow fiber membrane module of the present invention.
In addition, the above hollow fiber membrane is preferably such that the nitrogen transmission rate is 0.5-10xe2x88x929 cm3/cm2xc2x7Paxc2x7sec or more, and the oxygen transmission rate is 0.6""10xe2x88x929 cm3/cm2xc2x7Paxc2x7sec or more. Since this hollow fiber membrane has superior deaeration performance, it can be suitably used in the hollow fiber membrane module of the present invention.
In addition, the chemical deaeration method of the present invention is characterized by being a chemical deaeration method that removes dissolved gas in a chemical using a hollow fiber membrane module that uses the above hollow fiber membrane module. According to this chemical deaeration method, changes in chemical composition during deaeration treatment can be inhibited, and an uncontaminated, deaerated chemical can be obtained efficiently and with stability over a long period of time.
In addition, the chemical deaeration method of the present invention is characterized as being a chemical deaeration method that removes dissolved gas in a chemical using a hollow fiber membrane module wherein, the chemical contains a nonionic fluorosurfactant, and at least the portion of the hollow fiber membrane that contacts the chemical is made of polyolefin. According to this chemical deaeration method, changes in chemical composition during deaeration treatment can be inhibited, and an uncontaminated, deaerated chemical can be obtained efficiently and with stability over a long period of time.
In addition, in the chemical deaeration method of the present invention, the above polyolefin is preferably polyethylene, polypropylene or poly(4-methylpentene-1). Since these polyolefins exhibit little adsorption of nonionic fluorosurfactant, they can be used suitably in the chemical deaeration method of the present invention.
In addition, the chemical deaeration method of the present invention is suitable for the case of using photoresist or developing solution as the chemical.